水中高压放电气泡的实验研究

采用高速摄影方法对通过金属丝的水中高压放电所产生的气泡脉动现象进行了实验研究，发 现气泡脉动有以下基本规律：脉动参数主要取决于初始总电能大小，而与电容和充电电压的 具体取值关系不大；实验段脉动参数受池壁的边界效应影响很小. 气泡的脉动机械能占据了 放电总能量的20%—40%，第二次脉动与第一次脉动的能量比也与此接近； 喷射现象是造成 脉动能量减小的主要原因. 关键词： 高压放电 气泡 高速摄影     

用激光感生击穿光谱对大气进行定量分析

研究将激光感生击穿光谱技术用于元素定量分析的可行性。利用Nd∶YAG激光器发出的激光与一个大气压下的空气相互作用产生激光等离子体，等离子体的光经单色仪分光后转化为电信号进入计算机，存储了600～800nm的等离子体光谱数据。利用自由定标模型对等离子体进行了分析。在延迟时间8μs、采样门宽0.4μs时，利用二维波尔兹曼平面得到了大气等离子体处于局部热平衡时的温度（1.62×10K）。在假设空气全部由N和O组成的条件下由自由定标模型得到了空气中氧的含量（20.75%）和氮的含量（79.25%）。试验结果与实际吻合得很好。实验证实了用激光感生击穿光谱对大气进行定量分析是可行的，为大气污染监测研究和试验工作奠定了基础。     

New method of the directional modification of the electronic structure of single-walled carbon nanotubes by filling channels with metallic copper from a liquid phase

A method has been proposed and successfully implemented for filling the channels of single-walled carbon nanotubes with metallic copper by permeating with an aqueous solution of copper nitrate with subsequent thermal treatment. It has been demonstrated that the introduction of metallic copper into the channels of nanotubes leads to donor doping accompanied both by an increase in the Fermi energy of nanotubes and by the transfer of the electron density from introduced metal nanoparticles to the walls of nanotubes.     

Reconstruction of the signal produced by a directional sound source from remote multi-microphone recordings

A mathematical method for reconstructing the signal produced by a directional sound source from knowledge of the same signal in the far field, i.e., microphone recordings, is developed. The key idea is to compute inverse filters that compensate for the directional filtering of the signal by the sound source directivity, using a least-square error optimization strategy. Previous work pointed out how the method strongly depends on arrival times of signal in the microphone recordings. Two strategies are used in this paper for calculating the time shifts that are afterward taken as inputs, together with source directivity, for the reconstruction. The method has been tested in a laboratory environment, where ground truth was available, with a Polaroid transducer as source. The reconstructions are similar with both strategies. The performance of the method also depends on source orientation.     

Measurement of gas flow parameters by the laser produced breakdown method

A method of measuring gas flow parameters, based on testing the gas flow by shock waves, is described. The shock waves in the examined flow were produced by a pulsed laser beam focused on to the surface of an object. To illustrate the method, experimental data are presented dealing with gas parameters on the surface of a free-flying object.     

On the nature of the impulsive pressure produced by wire burst in water

It is shown that the impulsive pressure arising when a wire bursts in water is due to the products of a chemical reaction between the bursting wire and water. The dependence of the impulsive pressure amplitude on the bursting wire weight is satisfactory described by perfect gas laws.     

Spatial structures of spark channels in the breakdown phase

The cross sectional structure of spark discharges in the breakdown phase was investigated by means of anode evaporation patterns. Assuming the channel structure being determined by space charge effects reasonable agreement between computed initial channel diameters and experimental results was found.     

Nonstationary interaction of a supersonic flying object with extended low-density regions in the atmosphere

A three-dimensional numerical model is developed and the aerodynamic loads are determined for the three-dimensional flow acting on a blunt cone flying in the atmosphere along the boundary of a rarefied region, as functions of the degree of immersion of the surface of the body in low-density air. The nonstationary gas-and aerodynamic processes accompanying the entry and exit of the body from the rarefied region are studied. The aerodynamic coefficients obtained with an approximate model are compared with the three-dimensional calculations and found to be in satisfactory agreement with them. Zh. Tekh. Fiz. 68, 32–37 (November 1998)     

Statistics of breakdown centers during the propagation of laser radiation through a turbulent atmosphere

The statistics are examined for breakdown centers that arise in a polydisperse background aerosol during the propagation of intense laser radiation through a turbulent atmosphere.Translated from Izvestiya Vysshikh Uchebnikh Zavedenii, Fizika, No. 2, pp. 75–79, February, 1987.     

High-speed recording of laser- produced breakdown in air

A series of laser-produced breakdown interferograms has been obtained using five diffraction interferometers with pulsed ruby lasers serving as light sources. The interferograms and the results of their processing are presented in this article.     

Determination of copper content in soils and ores by laser-induced breakdown spectrometry

Features of electromagnetically induced transparency (EIT) in potassium vapors at the D₁ line of the ³⁹K isotope are studied. EIT resonances with a subnatural width of 3.5 MHz have been recorded upon excitation by two independent narrow-band diode lasers in a 1-cm-long cell filled with a natural mixture of potassium isotopes and buffer gas. The splitting of EIT resonances in potassium vapors in longitudinal and transverse magnetic fields has been studied for the first time. The splitted components also have a subnatural width. The smallness of the coupling factor of the hyperfine structure in ³⁹K atoms leads to a transition to the Paschen—Back regime at relatively weaker magnetic fields than in the case of Cs, Rb, and Na atoms. Practical applications of the phenomena under study are noted. The theoretical model well explains the experiment.